Art of polishing diamonds



UNITED STATES PATENT orrion.

CLYDE J. COLEMAN, OF NEW ROCHELLE, NEW YORK, ASSIGNOR TO STERN-COLEMAN"DIAMOND MACHINE COMPANY, INC., OF NEW YQRK, N. Y.

ART OF POLISHING DIAMONDS.

No Drawing.

1' b all whom it may concern Be it known that I, CLYDE J, COLEMAN, acitizen of the United States, residing at New Rochelle, in the county ofWestchester and State of New York, have invented certain new and usefulImprovements in the Art oi Polishing Diamonds, of which the following isa specification.

My invention relates to the art of cutting and polishing diamonds or theabrasive treatment thereof, and relates more particularly to the holdingof the diamond during the cutting and polishing operations or during thepolishing operation.

In polishing diamonds, it is the practice at the present time to holdthe diamond in the polishing tool by partially embedding it in a body ofmetal in a semi-molten state, contained in a small brass basin or dop,the diamond being held in position by the metal after the metal hascooled. This method suffers from the disadvantage that it is necessaryfrom time to time to soften the metal and readjust the diamond to eX-pose a different part thereof for polishing, as itis not possible toexpose at one time all parts of the diamond 011 one side of the girdleline; It is also common practice to lock the larger stonesin a clampingdevice, I

but this device is very difiicult to adjust so as to hold the diamond atthe correct angle.

The difficulty in holding diamonds during the polishing operation, asdistinguished from other precious stones, 1s due to the ex tremehardness of the diamond which ne- 7 cessitates applying great pressure,with re sultant great friction and generatiton of great heat; Diamondpolishing is particularly a difiicult operation and unlike otherlapidary work because with all other gems there is something harder thanthey are, which will easily abrade them andnot require any special speedor pressure to polish them, but the diamond being the hardest knownsubstance, it must be polished with its own dust. This requires greatlap speed,

great pressure and also a precise'grain presentation to the direction ofmovement of the lap, with the result that a high tempera-- ture isgenerated and often an. almost instantaneous risefrom low. red heattowh1te heat is developed when a hard spot is encountered Specificationof Letters Patent.

Patented Feb. 3, 1920.

Application filed. December 22, 1913. Serial No. 808,280.

and then a dropping normal red heat. Therefore a cement must possessresistance against the disintegrating effect of great enough to resistthe heat of polishing, must be strong and adhesive to resist thepressure and strain and must have substantially the same coefficient ofexpansion. or a requisite degree of thereof, so that its adhesion willnot be de stroyed or impaired by expansion or contraction due to suchtemperature changes.

The object of the invention is to provide an improvedmethod for holdingdiamonds in position for polishing, so as to avoid the disadvantage ofthe prior methods, and in particular to make it possible to polishallfaces of the diamond on one side ofv the girdle line without reclampingor resetting the diamond in its holder, thereby avoiding back suddenlyto the vibration, must be refractory.

elasticity which is equivalent the troublesome adjustments, calling forskilled manipulation, heretofore necessary. To these ends the inventioncontemplates may be polished without resetting or reclamping the diamondto thearbor.

I'liave discoveredthat an excellent cement for this purpose may beformed with a clay base or a base of clay and graphite compounded withsalts of metals, such as nitrates of metals, and specifically nitrate oflead and nitrate of antimony, and a boron'com-v pound, such as boracicacid or borax. These compounds are made into a thick paste, and for thispurpose the addition of a .suflicient quantity of water has-been foundsuitable.

This paste is applied between the stone and the'arbor, preferably beingapplied in'con siderable body so that it will be anchored in the arborand will'form a stemwithin thefarborfor adhesively holding the dia mond,and it is baked'with the parts to a cement having,

gether at a high temperature preferably in a non-oxidizing environment,as by inclosure in a retort containing carbon monoxid or hydrogen gas.The heat is first applied at a low temperature to dry the material, andthen at a high temperature. I have found that a temperature of 1800Fahrenheit is suitable for this purpose although a temperature as low as800 F. may be used. The total baking operation usually requires fromtwenty-five to thirty minutes. 'When thus heated and set the diamondwill not be loosened from the cement by the polishing operation on thediamond.

Specifically the cement which I have found to give the best resultscontains a base consisting of a material known as Dixons stove polish,this material being apparently composed of clay and graphite, and I haveat times replaced this stove polish by a mixture of clay and graphite,about 60% of clay and d0% of graphite and if desired somewhat more claymay be added. This base is compounded with the following materials inthe following proportions by volume: base, parts; nitrate of lead, 10parts; nitrate of antimony, 15 parts; boracic acid, 20 parts. Aconvenient way of mixing these materials is as follows: Take 50 parts bybulk of Dixons stove polish, selecting that which is dense, hard, and ofgood body and not friable, crumbly, sooty or of a dirty nature, and 50parts by bulk of pure, white, soapstone clay such as the talcum andsteatite' varieties, and 20 parts by bulk of borax or boric acid, and 10parts by bulk of nitrate of lead, and with these in finely dividedcondition mix them thoroughly. The nitrate of antimony is preferablyused in the form of concentrated solution prepared by allowing strongnitric acid to act on an excess of antimony for about ten to sixteendays, and this solution diluted by adding about an equal amount ofwater. The powdered mixture is then made into a thick creamy paste witha suificient amount of this nitrate of antimony solution. This paste isallowed to stand for twenty-four hours or longer, and then it is madeagain into a similar paste with water. The paste or cement is thenapplied between the diamond and arbor and baked as above described. 7

While my present invention is intended more particularly for use inpolishing diamonds, it may also be advantageously employed for thepreceding roughing out or bruting operation, thereby obviating thenecessity of the present practice of having to remove the diamond fromthe arbor employed in bruting and to attach and re center it on anotherarbor for polishing.

It is obvious that various modifications may be made in the hereindescribed specific embodiment of my invention, as by varying theproportions or by substituting chemical equivalents for one or more ofthe ingredients, within the scope of my invention.

I claim:

1. The improved cement for holding diamonds during the polishingthereof, by adhesive action, which cement has the physicalcharacteristics that it does not disintegrate or soften under the heatof the polishing operation, and has such a degree of elasticity that thediamond during the polishing may be rigidly held in place by the. cementapplied to the diamond on one side of the girdle, so that substantiallyall the facets on one side of the girdle may be polished, without--resetting or reclamping the diamond to the arbor.

2. The improved cement for holding diamonds during the polishingthereof, by adhesive action, which cement has the physicalcharacteristics that it does not disintegrate or soften under the heatof the polishing operation and has such a degree of elasticity that thediamond during the polishing may be rigidly held in place by the cement.

3. The improved cement for holding diamonds during the polishingthereof, by adhesive action, which cement has the physicalcharacteristics that upon baking it in con.- tact with the diamond itwill rigidly adhere thereto and does not fuse or soften under the heatof the polishing operation and has such a degree of elasticity that thediamond during the polishing may be rigidly held in place by the cementapplied to the 100 diamond on one side of the girdle, wherebysubstantially all the facets on one side of the girdle may be polishedwithout resetting or reclamping the diamond to the arbor.

4. The improved cement for holding diamonds during the polishingthereof, by adhesive action, which cement has the physicalcharacteristic that it will rigidly hold the diamond during thepolishing operation by adhesion thereto, and which contains clay andgraphite as a principal base and a binder, in the nature of an enamel.

5. The improved cement for holding diamonds during the polishingthereof, by ad hesive action, which cement has the physicalcharacteristic that it will rigidly hold the diamond during thepolishing operation by adhesion thereto, and which contains clay as aprincipal base and graphitic material and a binder.

6. The improved cement for holding diamonds during the polishing thereofby adhesive action, which cement has the physical characteristic that itwill rigidly hold the diamond during the polishing operation by adhesionthereto, and which contains graphitic and refractory material and abinder.

7. The improved cement for holding diamonds during the polishingthereof, by ad hesive action, which cement has the physicalcharacteristic that it will rigidly adhere to the diamond on baking withsuch tenacity as to hold the diamond during the polishing operation byadhesion thereto, and Which contains clay, graphitic material and abinder.

8. The improved cement for holding diamonds during the polishingthereof, by adhesive action, Which cement has the physicalcharacteristic that it will rigidly hold the diamond during thepolishing operation by adhesion thereto, and Which contains clay,graphitic material and a binder formed of a combination containingnitrate of antimony and a boron compound.

9. The improved cement for holding diamonds during the polishingthereof, by adhesive action, Which cement has the physicalcharacteristic that it Will rigidly hold the diamond during thepolishing operation by adhesion thereto, and Which contains clay,graphitic material, a boron compoimd and a binder formed of a solutioncontaining a salt of antimony in proportion such that, upon baking, thecement Will rigidly hold the diamond.

10. The improved cement for holding diamonds during the polishingthereof, by adhesive action, Which cement has the physicalcharacteristic that it Will rigidly hold the diamond during thepolishing operation by adhesion thereto, and which contains refractoryand graphitic material and a boron compound and a binder containingsalts of antimony and lead.

11. The improved cement for holding dia-' 60% clay and 40% graphite, 10parts nitrate of lead, 15 nitrate of boracic acid.

12. The improved cement for holding diamonds during the polishingthereof, by adhesive action, which cement has the physicalcharacteristics that it does not disintegrate nor soften under the heatof the polishing operation and has such a degree of elasticity as torigidly hold the diamond during the polishing operation, by adhesionthereto, and Which contains clay and carbon as the principalingredients, and a binder in the nature of an enamel.

In testimony whereof I have afliXed my signature in presence of twoWitnesses.

CLYDE J. COLEMAN.

antimony, and 20 parts M. M. ALcoRN.

